in OS_CPU_ExceptHndlr. The UART interrupt has the priority AT91C_AIC_PRIOR_HIGHEST, the other active interrupts (PIT and SPI) use lower priorities. The firmware uses three tasks, two mailboxes to communicty between ISRs and tasks, and one mutex for communication between two tasks.

On average, the latency (end of parity bit of received byte to start bit of transmitted byte) is about 12.3 us, however, the latency varies between 6.4 us and 20.4 us.